Circuit breaker



Jan. 7, 1936. T, UNDSTROM 2,027,238

CIRCUIT BREAKER Filed Nov. 26, 1950 mvENToR Q Tw@ md5 "from Patented Jan. 7, 1936 [UNIT-ED STATES PATENT .ol-Fics cmcUrr BBEAKEB i Ture Lindstrom. Edgewood. Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application November 26, 1930, Serial No. 498,408

`3 Claims. (Cl. 20o- 88) My invention relates to circuit breakers and particularly to circuit breakers and tripping mechanisms therefor that are current-responsive for tripping to open position under overload and short-circuit conditions.

An object of my invention is to .provide a tripping devicev wherein a bimetal thermal element serves to releasably retain a circuit breaker in operative closed position and wherein `a magnetic device, energized by the current passing through the thermal element, serves to deflect or move the thermal element to releasing position in' response to predetermined current conditions, such as are caused by a short circuit.

A further object of my invention is toprovide a thermal element for releasably retaining a circuit breaker in operative closed position wherein the operating characteristics of such element may be varied without altering its shape. I Y.

These, and other objects that will hereinafter appear are attained by means of the apparatus hereinafter described, and illustrated in the accompanying drawing; wherein,

Figure 1 is an elevational view, partially in suec-y tion, of a circuit breaker and trip mechanism therefor embodying features of my invention,

Fig. 2 is an'end elevational view of the trip mechanism shown in Fig. 1 and Fig. 3 is a transverse section through the trip mechanism, taken on line IIIg-III of Fig. 2.

Referring to the drawing, the circuitv breaker to which the improved trip mechanism is applied comprises an insulating base 4 uponl which is mounted a metal supporting frame 5, terminal contact Gand a terminal l; The movable contact arm 8 is pivotally mounted for oscillatory movement about the pivot shaft 9, and a springmetal contact varm Il is attached thereto by means of an attaching screw I2- which also serves to connect a flexible conductor I3 to the contact arm 8. The outer end of the spring member II is provided with acontact I4 that is secured to its free end by means of a rivet I which serves to clamp one end of the iiexible conductor I3 between the spring member and the contact.

The contact arm 8 is actuatedA by means of a pair of toggle links I5 and I6 that are pivotally connected together by a knee pivot shaft I1, the link I5 being pivotallyvconnected to the contact arm 8 by a pivot shaft I8 and the link I6 being pivotally connected to va cradle I9 by means of a pivot shaft 2I.- f

The cradle I9 is mounted upon the frame 5.101' oscillatory movement about a pivot vshaft 22, mounted on the frame 5; and is releasably re* contact I4 to open and to closed positions is, ac-

24 that is pivotally connected, at one end, to the 1c knee pivot shaft I1 and, at the other end, to a pivot pin 25, carried by an operating handle 26 that is mounted for oscillatory movement about a pivot shaft 21 which is supported by the frame 5.

' Clockwise movement of the operating handle 26 causes the center of the pin 25 to be moved beyond a center line of the pivot shafts I8 and 2l, which results in moving the knee pivot I1 laterally. This movement, by reason of the contraction of the spring 24, causes the toggle links to collapse and move the contact I4 to the open position shown'in dotted lines in Fig. 1, with a snap action. Upward movement of the operating handle 26 causes closing of the contact I4, when the 25 center of the pin has again moved 'about the said center line of the toggle pivots Il and 2I. When the cradle I9 is released, in response to an overload or a vshort-circuit condition, the contraction of the spring 24 also causes collapse of 30 the toggle when the cradle has moved the pivot pin 2| in a counter-clockwise direction beyond a center line through the knee pivots of the toggle and the pin 25.v Manual operation of the cordingly, accomplished through the movement of the operating handle 26, and automatic operation of the circuit breaker to open position occurs when the cradle I9 is released.

The trip device 23 for releasably retaining the circuit breaker in closed position comprises a ilat strip 28 of bimetal that is connected to the terminal 1 by means of rivets 29, which also serve to secure a bracket 3| thereto that supports an iron strap 32 to constitute a portion of a magnetic band surrounding the bimetal, in the manner indicated in Fig. 3. One .end of the iiexible conductor I3 is conductively connected to the bimetalelement at a point between the free end thereof and its point of attachment to the terminal 1, the conductor I3 being attached to the bimetal element by screws or rivets 33 that also serve to attach a metal strap 34, which constitutes aportion of the iron band previously referred to.

By attaching the conductor I3 to the bimetal 55 strip 2s, at a. point intermediate its ends, ,au of the current may be made to pass through the bimetal element at any desired point between the point of attachment of the conductor I3 and the xed end of the strip, thus causing the heating eiect of the current to be concentrated between the point of Yattachment of the metal strip 28 to the terminal 1 and the iiexible conductor I3. The maximum bending of the bimetal element, at that point, will, therefore, cause a relatively wide range of movement of the free end of the bimetal which carries a latch clip 35 that is insulated from the bimetal strip by an insulating plate 36, and releasably engages the latch arm 3l of the cradle I9. The strip is provided with a plurality of perforations 40 for permitting attachment of the conductor to the strip at any desired point.

Under normal operating conditions, the bimetal strip will remain in the latch-retaining position shown in Fig. 1 and will releasably retain the circuit breaker in closed position. Under an overload condition, the bimetal element will `be heated by the excessive current passing therethrough andlcause it to deect to the brokenline position shown in Fig. 1, wherein the latch 35 is disengaged from the latch 31, thereby causing the circuit breaker to be released or tripped to open position, wherein the latch and cradle will occupy the positions shown in broken lines in Fig. 1.

The iron strap 32, which is of U-shape, partially surrounds the bimetal element 28, and, in

magnetic circuit in it to cause the strap 34, whichv constitutes an armature, to be moved into en-v gagement with the ends of the iron strip 32,' by

reason of the magnetic flux which tends to close the air gaps. Since the strap 32 is stationary, the

strap or armature 34 causes deection of the bimetal element instantly upon the occurrence of a short-circuit condition and thereby causes instantaneous opening movement of the circuit breaker. f

The trip mechanism, therefore, provides al time interval before opening the circuit breaker under overload conditions, and an instantaneous trip under short-circuit conditions, and, by connecting the exible conductor I3 at any one of thev various points between its iixed and its free ends,

the time lag or the current rating of the bimetal element may be varied without altering its shape. The bimetal current-responsive element, therefore, may be calibrated by simply shifting the position of the flexible conductor with reference 'to it. 5 While I-have illustrated but one embodiment of my invention, it will be apparentto those skilled in the art that various changes, modifications, substitutions, additions and omissions may be made in the apparatus illustrated, without de- 10 parting from the spirit and scope of my invention, as set forth in the appended claims.

I claim as my invention:

1. In a trip device for a circuit breaker, a conducting means having a pair of electrical termi- 15A nal members connected in circuit with said circuit breaker and including a portion heated by the ow of current therethrough, and movable means of bimetallic material joined to the heated portion of said conducting means to permit' flow 20 of heat by conduction from said heated portion to said bimetallic means to cause deection thereof to trip the circuit breaker, and means including a member of magnetic material aihxed to said movable means and energized by the flux 25 set up by the current iiow in said heated portion to deect said means of bimetallic material to tripthe circuit breaker.

2. An electro-responsive means for electrical apparatus comprising a conducting means having a pair of electrical terminal members and a heater portion therebetween, a bimetallic member having a portion conductively joined to the heater portion of said means to permit ow of heat by conduction from said heater thereto, said bi- 35 metallic means having a freely movable portion, and a magnetically responsive means including a member of magnetic material afxed to said freely movable portion. p

3. In an lelectro-responsive trip mechanism for 40 electrical apparatus, conducting means having a pair of electrical terminal members and a heater portion of bimetallic material electrically connected therebetween, said heater portion of biof said heaterportion of bimetallic material to actuate the electrical apparatus.

v TUBE LINDSTROM. 

